…Some fish, some barrel

I’m afraid he’s at it again. Wishart, that is. It seems he can’t stop himself from reading Hot Topic and then posting his reactions. In his latest excursion, he reads a comment of mine, and then feels the need to once again demonstrate the depth of his understanding. He begins thus:

Can you believe the chutzpah? The thing that gets me about climate Chicken Littles is the way they repeat bogus claims ad nauseum as if trueâ€¦ this comment from Gareth Renowden at Hot Topic tonight illustrates ignorance on this point:

“In deep time, there have been periods when CO2 has been higher than now (how much higher is a matter of study), but lots of CO2 is inevitably associated with a warmer planet.”

Invariably?? The blue line is temperature, the black line is CO2:

And he whips out the chart you see above (click on the thumbnail to be taken to the source). It features (without credit to source) on page 34 of Air Con. He continues:

I defy anyone, including Renowden, to find a pattern in the historical record that proves CO2 is “invariably” associated with a warmer planet. It will be especially hard for him as the ice cores all show CO2 rise lags temperature increase by several hundred years, not precedes it.

I didn’t have to try very hard to defy Wishart, because the “pattern” is well-established in the literature:

A pervasive, tight correlation between CO2 and temperature is found both at coarse (10 my timescales) and fine resolutions up to the temporal limits of the data set (million-year timescales), indicating that CO2, operating in combination with many other factors such as solar luminosity and paleogeography, has imparted strong control over global temperatures for much of the Phanerozoic.

That comes from the abstract of Dana Royer’s 2005 paper, CO2-forced climate thresholds during the Phanerozoic (PDF). The paper’s worth a read if you want to understand some of the complexities of deep time and climate, but John Cook at Skeptical Science provides an overview here. Royer’s paper was published well before Air Con, so one has to wonder how it managed to escape Wishart’s attention…

The graph that Wishart relies on comes from this page at a site notable for its sceptic stance, and has been widely used around the crank sites — including microWatts. It appears to be a mash-up of a CO2 data series (there are several — there’s a better graph here; note there’s one reconstruction that doesn’t suggest high CO2 levels 500 mYa), with a schematic of temperature from this site — the rather interesting Paleomap Project. Note that the temperature schematic has been rotated through 90Âº, re-scaled and re-drawn to fit over the CO2 graph. It’s reminiscent of the sort of graphical jiggery pokery practised by Monckton… But it’s good enough for Wishart, who devotes several pages to over-interpreting the ups and downs of the lines in chapter three of Air Con (pps 34-36).

What happens if you do the exercise properly? Refer to the Royer paper. It doesn’t have the pretty colours, or one single equivalent graph, but it does have a properly nuanced discussion of the relationship between CO2 and temperature over the last 540 million years:

…given the variety of factors that can influence global temperatures, it is striking that such a consistent pattern between CO2 and temperature emerges for many intervals of the Phanerozoic.

A good enough pattern for me.

Wishart also mentions the so-called “lag” between CO2 increases and temperature increases during ice age terminations, as if this somehow changes the radiation physics of CO2. He appears unable to understand that the gas can be both feedback and forcing. During ice age terminations, it’s a feedback to orbital changes that becomes a forcing. Today, it’s a forcing – and we’re doing it. More at Skeptical Science.

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69 thoughts on “…Some fish, some barrel”

Looks like R2D2 needs to look up young faint sun paradox. Climate is multi-factor. TSI was lower when earth was younger, and reconstructing the thermohaline circulation in the distant past is quite a challenge.

This graph (link above) shows an ice age beginning 300,000 years ago while CO2 was higher than current levels.

No, it doesn’t. Current CO2 levels are the highest for at least 3 million years. The most recent interglacials have topped out at around 300 ppm. That wasn’t enough to counterbalance the orbital cooling, but that was with a biosphere with minimal human impacts.

Please post the study which makes you believe this exact same event can not happen again.

The answer, of course, is that if you look at something other than the dubious graph upon Wishart relies, you see that warm periods are associated with high CO2 and cool/cold with low. That’s what Royer’s paper (and others) shows. Why not start by reading that?

Actually for planetary temperature (any planet), it basically a function
of TSI (or luminosity of star and distance from that star), albedo, and green house gas effect. Estimating past CO2 (beyond ice core range) has its own problems, but minor compared to estimating albedo in past. TSI can be estimated to vary roughly through geological time with evolution of the sun as standard series star. The trouble with predicting climate when you change something (like greenhouse gas composition), is that albedo, temperature, and GHG composition are not independent variables but vary together because of feedbacks. Modelling these feedbacks in deep time with a mass of other poorly constrained variables is tricky. Thomas Crowley does a pretty good job with a simple model for the pleistocene.

When you look at the GEOCARB III paper, it’s immediately apparent that their model utilises the results of GCMs, among other things. In approvingly citing it, is Wishart acknowledging the usefulness of climate models?

I’ll give Wishart his due — he is obviously one of our more regular, if anonymous, readers. He’s updated his original piece, and manages to suggest that Royer 2005 is somehow trumped by a paper published a year earlier by Israeli cosmic ray enthusiast, Nir Shaviv. Since physics is malleable in Wishart world, perhaps he has a time machine…

Figure 2 Variations in regional surface temperatures for the last 18,000 years, estimated from a variety of sources. Shown are changes inÂ°C, from the value for 1900. Compiled by R. S. Bradley and J. A. Eddy based on J. T. Houghton et al., Climate Change: The IPCC Assessment, Cambridge University Press, Cambridge, 1990 and published in EarthQuest, vol 5, no 1, 1991.

R2D2 – be sure to follow Thomas Crowley’s more recent publications as well. I dont think you will find any comfort. Tom’s simple feedback model does a remarkably good job of modelling pleistocene climate and gives us an ugly future.

One of the things I find most frustrating about this whole thing is all the different versions of the past, it is quite Orwellian really. And for a layman like myself it hard to know what one to trust. There are even different versions of the present!

For me a key question is, how does todays climate compare to the past?

If people could post alternate histories (that is a worrying question), and explain why they are superior to the one I posted I would be interested in finding out more.

Currently I see warm periods and changing climate throughout the current interglacial (not just the medieval warm period but the Roman and Bronze age warm periods as well) and think, how can we know that todays changes are not simply part of the natural climate variation? If the climate always changes, why should we spend resources trying to prevent ‘climate change’? Why not simply be aware that what ever we do the climate will change and we will need to adapt?

Compare the 1991 graph with this one:
Two things should be obvious (note the two cover different timescales): rapid warming out of the last ice age, followed by a warm hump 6 – 8k yrs ago, and then a cooling. Both graphs omit the upward tick at the end of the series that gets us to current temperatures.

So: we have a 1991 graph based on the best of our knowledge at the time, and one prepared nearly 20 years later, based on a considerably expanded knowledge base. Should we ignore the work that’s been done in the last 20 years, and rely on someone’s best guess in the late 80’s. early ’90s? That’s not admitting to “alternate histories” — it’s accepting that a lot of work has been that throws light in the big picture. We don’t (and never will) have perfect knowledge of past climates, but we can learn more and improve our understanding. Are we supposed to ignore advances in understanding because they’re somehow politically inconvenient?

If you want to know more about the study of paleoclimate, I suggest you find a good textbook and start there, rather than try to ignore the stuff we know.

As for natural variations, what’s natural about a 40% increase in CO2 in the atmosphere? We did it. Physics tells us it will warm the planet.We observe the planet warming. Done deal, to all intents and purposes, unless you wish to argue with the basic physics of CO2 in the atmosphere, or the source of the accumulating CO2. If that’s what you want to do, well and good, but don’t complain if people write you off as a fool.

In terms of the graph you posted, the year 2004 is marked on the graph. Do you know if this was based on the same proxies used in the reconstruction, a satellite temperature splice, or a splice of a non-peer reviewed compilation of land based temperature stations? If it is not based on the same proxies, how can we compare this readings to the past?

Others have asked that graphs be sourced, what study was this graph from? Was the 2004 data point included on the study, or added on by an author at Wikipedia?

If you click on the image, it’s linked to the source page, which explains how it was put together. The 2004 number is there as an illustration, not as a part of the reconstruction. It shows that we’re probably already as warm (or warmer) as the warmest part of the Holocene

For starters, it is one year and you are comparing it on a line that is obviously smoothed – there could have been years in the past warmer than 2004 but they would have smoothed of into a trend line. It is also a temperature reading compared to a proxy for temperature. What you need to show is a proxy reconstruction that shows modern temperatures are warmer than the past, and then explain why the 1990 version ‘got it wrong’.

“Why not simply be aware that what ever we do the climate will change and we will need to adapt?”

That’s an interesting attitude R2. Do you just apply it to climate or to all issues that face mankind. Let’s see……..

Medicine – we know that people have always suffered from disease, should we try and understand why the diseases arise and see what we can do to prevent them – or, shall we just adapt, let a few (million) die and breed some more to replace them.

Avalanches – should we let the tourist buses play russian roulette on the Milford Road each winter – or should we try to understand the physics behind the avalanche danger, use computer models to assess avalanche risk and take preventative action (set a few off, close the road occasionally).

R2D2 – welcome to the issues of paleoclimate. As you go backward in time, then uncertainties mount. Beyond icecore, you are reliant on proxies for CO2. Beyond historical records, you are reliant on proxies (Oxygen isotopes) for temperature. Everything in geology has dating issues. The net result of this is really that you have unconstrained models to deal with. Its not a case of “cant explain this” – its more a case of there are multiple ways to explain it and not enough data to be really sure of one or the other. So it IS possible that this is some natural cycle that we havent found yet – but that is not the way to bet.
Climate changes for a REASON. Underlying all of this is physics – changing temperatures mean changes in the energy budget somewhere. The point of the papers published so far, is that you dont need some deep mysterious unexplained cycle to account for what you see in paleoclimate data. What we know works very well but there can be multiple models to account for data – especially when you go back far enough that the land/ocean distribution is significantly changed. But for the present day climate, we can follow the energy budget quite well. Sun increasing? nope, minimum on an 11 year cycle, cooling on a 10,000 year cycle, warming on a billion year trend. And if its the sun, then why tropospheric warming and stratospheric cooling?. Aerosols – well these have a part to play – volcano eruptions and paleoclimate are valuable for constraining these. GHGs well – looks like a smoking gun to me. It is certainly the way to bet and if you care about grandchildren, then its the most important bet you are likely to make.

“One of the things I find most frustrating about this whole thing is all the different versions of the past, it is quite Orwellian really. And for a layman like myself it hard to know what one to trust.”

Well you certainly make it difficult for yourself when seem to decide in advance not to trust those who know what they are doing.

“It is also a temperature reading compared to a proxy for temperature. What you need to show is a proxy reconstruction that shows modern temperatures are warmer than the past, and then explain why the 1990 version â€˜got it wrongâ€™.”

Umm, funnily enough proxies are calibrated and/or checked by comparing that measurement to direct measurement so that is reasonable. The 1990 version is not so much “got it wrong” – as best interpretation with available data. We have more data, better methods.

Temperature proxies are used to compare climate changes overtime. The proxy is reconciled against readings and the magnitude of those changes are calibrated by looking at the part of the proxy we have instrumental record for, but to make the statement, ‘1998 is the warmest year in the last 1000 years’, you would need a proxy record that covered the last 1000 years and that showed 1998 as the most extreme event of that proxy record. Otherwise it is just bad science.

I believe this was the case for the graph Gareth posted, as none of the proxies are shown to spike in the late 20th century. However I am awaiting an explanation.

The below proxy shows that modern temperatures are the warmest, however the data does not reconcile well with known history or AGW theory (as there is no MWP or LIA, and most of the warming occurs too be CO2 driven)

I am not biased in my interpretation of science, I am here discussing temperature histories on a post that’s topic is past histories. I am genuinely wanting to get to the bottom of this. Maybe it is you who is biased towards histories that do not validate CO2 forced warming?

In response to a request from Congress, Surface Temperature Reconstructions for the Last 2,000 Years assesses the state of scientific efforts to reconstruct surface temperature records for Earth during approximately the last 2,000 years and the implications of these efforts for our understanding of global climate change. Because widespread, reliable temperature records are available only for the last 150 years, scientists estimate temperatures in the more distant past by analyzing "proxy evidence," which includes tree rings, corals, ocean and lake sediments, cave deposits, ice cores, boreholes, and glaciers. Starting in the late 1990s, scientists began using sophisticated methods to combine proxy evidence from many different locations in an effort to estimate surface temperature changes during the last few hundred to few thousand years. This book is an important resource in helping to understand the intricacies of global climate change.

Oh really? If that was the case, you wouldn’t use words like “splice”, which clearly indicate that you have decided that any temperature graph which doesn’t match your pre-conceived notion of a MWP that is warmer than today must be false.

R2D2, if you want anyone to look at a graph or chart, you need to post a link which also has the discussion. Not just the image. Especially when it has no axis labels, or source data. It’s effectively meaningless.

And we had the hottest August – do stop trying obsessing about the weather. AGW theory is about climate. What does it take to get that through. Oh, thats right you think climate models that show non-monotonic warming are faked and produced in response to a few La ninas.

I bet the next time we have an ‘unusually’ hot day, the alarmists will be crowing that it’s clear evidence of global warming. But the next unusually cold month will be just “weather”. In any case it wasn’t just October that was unusally cold. There have been seven such months this year with unusally low temperatures, not to mention the last few years with similarly unusually cold winters, esp in the northern hemisphere. You’ve only got August 2009. That suggests an overall downward trend to me.

So who’s confused about weather and climate?

As for Rob Taylor, at least you’re consistent with your non-sequiturs like Stern and co who link climate change to vegetarianism! So you’re in good company there.

Boy, am I sick of reiterating this. CLIMATE is about a 30 year trend. The models predict what happens on a 30 year trend. And yes, modellers are working very hard to refine the physics to be able to predict decadal trends as well. The Keenlyside, Latif is one result, (which predict little warming till 2015) but noone taking bets on it because these predictions are much harder (working out distribution of heat rather than total heat budget).

If you are so keen on weather cycles, are you going to suddenly become an AGW advocate when the decadal cycles go positive and back to a denier when they go negative again?

And PLEASE, PLEASE stop confusing scientists with environmental activists. Climate scientists are less impressed by weather and also stop confusing local weather with global weather.

Vegetarians? Well from memory, serving up meat costs 15kWh/p/d whereas vegies only require 8kWh/p/d plus need a lot less land. You dont “save the world” by going vege but it could help.

If you want to invalid AGW then you need to look at its key predictions.
1/ 30 year trends will rise
2/ troposphere will warm, stratosphere will cool
3/ arctic warming (but not antarctic) will be amplified.

These are what the models actually predict. Try attacking those instead of a host of straw men.

AGW-Denier, what you post are the standard, weak, denier talking points which only those who have little understanding of the science would actually post. Not understanding the difference between weather and climate, and pretending that scientists claim things when they don’t, are fairly basic indicators. The strength of your opinion seems proportionate to your lack of understanding and your unwillingness to do your own research and relieve yourself of ignorance. Which is, again, very common with deniers. it’s a political argument to most deniers – they don’t actually care at all (and therefore are never able to argue rationally) about the science.

R2D2. Good for you in wanting to get to bottom of this but you may find the paleoclimate data frustratingly incomplete. Working up a world-wide temperature average from instrumental data is controversial enough. Now do the same for climate proxies. Paleoclimate can constrain our models, and it could invalid them, but I suspect the precision you are expecting is not there yet. You can find a lot of very useful explanation herehttp://www.realclimate.org/index.php/archives/2004/12/myths-vs-fact-regarding-the-hockey-stick/

Dont think its about Mann v McIntyre controversies but its about a number of other misconceptions. (I worry about what you understand LIA and MWP to mean), and especially about the limits of this data. Really full discussion in the papers listed in the bibliography. Have you actually read the IPCC summary of this stuff?

It might give you some idea of the difficulties with proxies and distinguishing between global and local climatic events.

Perhaps from a local context you might like to figure – when was the last time that the Tasman Glacier terminus was in its current position?
AT NO TIME IN THE LAST 26,000 years. It might have been further back in previous interglacials, but you are talking a very long time ago.

Now you see this is what Iâ€™m talking about. You keep missing the point.

I am merely using the same argument you guys use all the time, but in reverse. So Iâ€™ll explain in more basic terms: Whenever there happens to occur a hot spell, like a heat wave or an unusually warm day or week that is warmer than â€˜averageâ€™, the alarmists seize on it and immediately put it down to global warming. It is trumpeted as evidence of AGW and the â€œ30-yearâ€ trend criteria doesnâ€™t seem to apply. But if the reverse happens and we have a severe winter (like 2009 and the years before, esp in the northern hemisphere), or a month with lower than average temperatures, or even ten consecutive years with generally declining temperatures world-wide, the alarmists invoke their â€œ30-yearâ€ trend criteria and discount it as invalid because it is merely a â€œweatherâ€ event of short duration. The alarmists are happy to accept any short-term event (ie., way less than 30 years!) if itâ€™s warming (like for instance scaddenp citing August 2009 as a warm month – hence AGW), but anything less than 30 years is ruled out if itâ€™s a cooling period.

Interestingly, we had thirty years of cooling in the seventies and cries of alarm over an imminent ice age. But what was CO2 doing in the period? Was it increasing or decreasing (according to Mauna Loa)? Yes it was increasing while temperatures were going the other way! So much for CO2 FORCING!

What on earth are you talking about? The POSSIBLE significance of a hot august is that occurred despite deep solar minimum which doesnt augur well for solar hypothesis, (compare temps over this solar minimum with last solar minimum), however my real point is that cold october is no more significant than a hot august. AGW is only about trends.

You repeat the nonsense of 70s ice age despite it being pointed out before that this is nonsense with actual data. And again, climate is not single factor – the models fit the seventies temperatures with real physics quite well but I’ll bet you have never bothered to look or try to understand why.

If you dont look at contrary evidence or ever learn anything then argument is pointless. What are you hoping to achieve pushing out long debunked rubbish time and time again?

>>>>Whenever there happens to occur a hot spell, like a heat wave or an unusually warm day or week that is warmer than â€˜averageâ€™, the alarmists seize on it and immediately put it down to global warming. <<<>>>even ten consecutive years with generally declining temperatures world-wide<<<>>>cries of alarm over an imminent ice age<<<<

You need to do your own research about that – you'll discover the global cooling thing wasn't really anything much at all (and has been blown out of all proportion by the denial industry). There was a Newsweek piece and a Times cover. And not much more. Certainly almost no support in the scientific community. In actuality, there were significantly more papers in the 1970s predicting warming (42) than cooling (7).

Hahaha, nice….
Speaking of which I see even the CEI has now abandoned James â€œthe last flat-eartherâ€ Inhofe. In their 31-page testimony to the Senate, CEI never challenges the science while warning inadequate policies threaten â€œthose who will suffer the consequences of global warming”.
*falls off chair*

For the benefit of the ant at the picnic, Stephen Hill, what I was referring to was the thirty years of cooling from 1940-ish to 1975-ish. It’s commonly referred to as and known as the seventies cooling period.

Is this how you debate? You waste everyone’s time splitting hairs and being pedantic. Good job.

As for Taylor who thinks there is no debate going on: What does 31,500 scientists in the US alone who are skeptical mean? Maybe you think they don’t exist. Try http://www.petitionproject.org/

CM, on the graph that I posted, it is the non instrumental part of Mann et el 1999. (ie the graph minus the instrumental record)

CTG: Sorry I do not know how the observation that the Mann et el hockey sticks and spaghetti graphs are splices of proxies and instrumental records shows a non-AGW bias. Perhaps reality has a non-AGW bias and you need to come back from where you are (that is defiantly not reality)?

scaddenp: I read through your real climate link. Sorry on this I will show my bias. I really do not trust opinion pieces by real climate. They are well known advocates from AGW, as is Michael Mann. Surely there are other paleo-criminologists in the world than Michael Mann that you can turn too? Sorry if you trust the guy but to me he seems to have a bias – take his East Antarctic study for example.

To avoid an ad homien attack I will justify my displeasure in the article you posted: The link you posted is a blatant straw-man attack. It sets up a ‘myth’, and then disproves it. This is a weak form of argument and is easy to do to any opposing position.

For example:

“Alarmist Myth 1: Polar Bears are drowning an rates never before seen in history.

Blah blah blah easy disapproval

Alarmist Myth 2: Malaria will kill millions in a few years

Blah blah again”

This form of argument does not prove ones perspective correct, it just shows how easy it is to burn a straw-man.

If you can find somewhere where I have held the position of any of the myths in Mike’s opinion piece then I will stand corrected, but I think they are ridiculous pieces of slander that very few non-AGW believers would hold to be true.

“CM, on the graph that I posted, it is the non instrumental part of Mann et el 1999. (ie the graph minus the instrumental record)”

Yeah but can you give the context (the page it is from, rather than the seperated image).
I can tell it’s from the National Center for Policy Analysis (a hard-right think-tank), but I can’t find the page.

“scaddenp: I read through your real climate link. Sorry on this I will show my bias. I really do not trust opinion pieces by real climate. They are well known advocates from AGW, as is Michael Mann. Surely there are other paleo-criminologists in the world than Michael Mann that you can turn too? Sorry if you trust the guy but to me he seems to have a bias â€“ take his East Antarctic study for example.”

What is about the actual science that you don’t find credible? Play the ball, not the man (e.g. I haven’t dismissed your graph simply as NCPA propaganda, I’ve asked for more information so I can determine if it’s credible or not).

I’ll be honest, I don’t have the skill’s, knowledge, or time to go through one of his papers and prove it a falsehood (when I do read his papers, and other scientific papers on all issues, I often find that not all the data, methods and calculations are in the paper).

Things like this raise my eye brows though (I know it is only a media article):

“I do not know how the observation that the Mann et el hockey sticks and spaghetti graphs are splices of proxies and instrumental records shows a non-AGW bias.”

Your starting assumption is that the hockey stick is a fraud, and you don’t see how this indicates bias? Right.

Using the word splice just shows that you don’t understand how the proxies are constructed, and makes you look a bit of a fool, really.

You are trying to imply that the temperature record has to be squished and squeezed onto the proxy record, that it is really showing something else.

However, the point about the proxies is that they are calibrated to the instrumental record, so of course it is okay to draw the instrumental record on top of the proxies. There is no “splice”.

But then, you just can’t be arsed actually learning the science, can you? You are happy just to buy into McIntyre’s bullshit, and go round spouting allegations of fraud, rather than have to deal with the unpleasant reality that your personal, individual actions might be having a bad effect on the planet.

Look at the paper. Look at Figure 1 the proxies. No dramatic rise at the end. Look at the final graph (figure 3): dramatic rise! Where has this come from?????? The ground based instrumental record?? Wow! So what are we saying?? What are we comparing?

Did you actually read the paper, or are you just relying on what blog science has told you is in it?

Figure 1 is not the temperature reconstruction. It shows that there is a non-climatic influence in one of the principal components used (ITRDB PC#1), probably from CO2 fertilisation. Look at Fig. 1 – the upper graph shows that from 1800, ITRDB PC#1 is above (i.e. warmer than) the North American Treeline (NT) series. The lower graph shows just the difference (residual) between ITRDB PC#1 and NT – you can see that it follows the CO2 quite closely for a while, and then tails off.

What this graph is showing is that ITRDB PC#1 is showing even more recent growth than the other series, because as well as responding to warmer temperatures, the trees in that series are also showing more growth due to CO2 fertilisation. If you were to treat all of that recent growth as if it were due to temperature, PC#1 would be overestimating the temperature of the 20th century

So what they did was remove the residual from the ITRDB PC#1, so that it more closely matched the NT series. If the had not removed this residual, the PC#1 series would show an even more pronounced hockey stick – and I’m sure you wouldn’t want that, would you?

Then Fig. 3 shows the final temperature reconstruction using the corrected ITRDB PC#1 – remember, this is just one of 12 series they use in the reconstruction. As I said before, the temperature reconstruction is calibrated to the temperature record, so of course the series in the calibration period matches the instrumental record. If it didn’t, it wouldn’t be much use as a proxy, now would it?

Finally, remember that there is never a final answer in science. Look at the title of the paper: “Inferences, Uncertainties and Limitations”. Mann never claimed that this was the final word, and quite explicitly says that the period before 1400 is uncertain, as the full quote shows:

Though expanded uncertainties prevent decisive conclusions for the period prior to AD1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 was the warmest year, at moderately high levels of confidence.

Several papers since then, by Mann and by others, have confirmed the hockey stick, some with different techniques. Mann’s recent paper showed that you get the same results with or without the tree-ring proxies.

But if you are determined to believe in conspiracy theories, there is no amount of scientific evidence that is ever going to change your mind.

R2D2, the confident rants of deniers like Booker impress you, but you can’t bring yourself to approach respected climate scientists like those who contribute to RealClimate because someone has told you they are “advocates” of AGW. I suspect the commenters who have been patiently trying to assist you in this thread are working with a pupil who won’t do any homework. Climate scientists don’t advocate AGW, they have discovered it, usually to their own as well as our dismay. They report what they discover. You don’t have to read scientific papers to find out what it is – it’s available and accessible to the lay reader in any number of the books reviewed here on Hot Topic. Try leaving your scanning of denialist websites for a few days and just read one book – Wallace Broecker’s Fixing Climate, say, or David Archer’s The Long Thaw.

R2D2 – my apologies for not being more specific. What I thought might be useful to you on that page was the comments concerning

” The “Hockey Stick” studies claim that the 20th century on the whole is the warmest period of the past 1000 years.” which talks a little around the problem of what proxies can show. Crowley’s paper and Rutherford’s also illuminating since you clearly have some misconceptions about how proxies are constructed.

However, I am left in a quandary. You are obviously impressed by Bookers uninformed rave but dont trust the work of climate scientists? This makes it very difficult to have a discussion. You have trouble following the actual papers, you dont like explanatory pieces about the science (the are NOT opinion pieces) if they are written by climate scientists because climate scientists are AGW advocates (reality advocates would be better) and yet trust looney tunes stuff in a opinion piece from someone who is clearly clueless about the science.

If we cant present science papers as evidence, then how do we proceed? If you want your questions answered, then I will do my best but that must happen in the context science and data.

Let me see if I can recap because I think the argument got lost somewhere along away as it wondered into paleoclimate. Is current era unique? Well depends on timeframe. Is it different from LIA,MWP type events – yes. Firstly its not regional, and second explain say the Tasman glacier position. Are we beyond ice ages. Now thats a more tricky question. The milankovitch cycles which drive the ice ages were still working even when CO2 was high enough that we had no ice caps. Once planetary temperature dropped to point where ice formation at the poles was possible then this allowed for albedo feedbacks to kick in. Without feedback, the forcings from milankovich cycles would still have had some effect on climate but very small. I would say that you break the ice age cycle when+ve GHG forcings is greater than -ve TSI forcing. I’d say that paleoclimate data for what the world looked like with 450ppm CO2 is pretty ugly re: ice cap though greenland and East Antartica would take in order of 1000 year to melt.

Disclosure: I am geoscientist working in hydrocarbons section. If the world lost interest in oil/gas/coal our section would cease to get funding.

Sorry I was trying to post a reply quick – I do not place faith in the news paper article, I should research the paper on east antarctic temperatures. I was simply outlining the numerous controversial papers that Mann has co-authored. I agree this does not make them wrong, or Mann a lier. But it does lead me to seek non-Mann authored climate histories to back-up Mann’s work before I can gain complete trust.

As with MBH98 this is an astounding revelation. A paper has claimed that what everyone else held true, is wrong! This does not make the paper false of course. But a sceptic will always look at this new discovery with a critical eye.

I am not sure to be honest on the merit of this paper. It claims a 50 year warming trend.

This paper claims a current increase:
“We show that 72% of the Antarctic ice sheet is gaining 27 +/- 29 Gt / yr, a sink of ocean mass sufficient to lower global sea levels by 0.08 mm / yrâ€³

In response to the Antarctic paper, “A disbelieving Ross Hayes, an atmospheric scientist who has often visited the Antarctic for Nasa, sent Professor Steig a caustic email ending: “with statistics you can make numbers go to any conclusion you want. It saddens me to see members of the scientific community do this for media coverage.””

So whats my point here? I do not know the truth(and I am not trying to start a debate on the Antarctic). But given the controversy surrounding much of his work I can not help but raise my eyebrows when the only references people can find come from Real Climate and Michael Mann. I think if there was one predominant author who repeatedly published papers that cast doubt on AGW theory you would be skeptical also? (as would I). You would want to see other sources to reconcile the claims?

Whoops! I dont like it when other people overstate science so let me correct the position on the Tasman Glacier. We have no EVIDENCE of the tasman glacier being as far back as its current position in the late holocene. You cannot exclude the possibility however that it was not further back during the bronze age, 3000 years ago.

Fair enough I guess. Mann comes in for stick because he is very high profile though I think Steig is the main author of the paper you are referring to. Actaully much of that controversy played out at RC. RC DOES you a pretty unique opportunity – you can learn and ask questions of the people actually doing the science and civil questions get a civil response. In response to your wanting other papers, well the IPCC “the scientific basis” remains a great resource for finding the science even you might not like the politics. The Hockey stick does not rest on Mann – his was the first. You can find other studies by other scientists with different proxies and methods listed there. The most recent is Tingley and Huybers, (may not actually be published yet – I saw prepress) though their method is so different, I would expect it come under a great deal of scrutiny. http://www.people.fas.harvard.edu/~phuybers/Doc/mean_variance.pdf
Figure 4 at end perhaps?

I will say again, though that paleoclimate is hard with so much work still to do. However, unconstrained is not same as unknown. Can you reiterate for me exactly what you are looking for and why?

AGW looks to paleoclimate for constraints and hypothesis testing but it is a theory arising out of physics not geology.

Thanks, I have had a quick look at paper. Will have more of a look tomorrow / in the next week (Im busy at the moment – hence the one or two posts a day).

What I am after… interested to know why and how understandings of past climate (last 14,000 odd years) has changed since the first assessment report (graph that I posted earlier).

I would prefer pure proxy histories rather than a proxy-instrumental record combo, the link you posted is pure proxy so thanks on that count.

Yes understand that past climates do not prove or disprove AGW. I have actually always had an interest in history, find it interesting to understand the connection between climate and historic events. But also would like to put the current warming in a historical context.

Change in understanding since first report? Wow, lets see. We have the development of the boron proxy for CO2 and the subsequent deluge of data, multiproxy methods, the deep greenland and antarctic ice core for starters.

You will hate this, but you really should read IPCC chapter 6http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Print_Ch06.pdf
Its only one chapter and you dont have accept any of their assessments. It does however give you all the grubby detail in a much more readable format than trying to find the significant papers. It also put the papers in a context, that means if you want to be critical, you can know what went before and after. And of course, its exhaustively referenced to the papers so you can check anything.

Some comment. The ice cores are very high time resolution, better measurement of CO2 than any proxy, and state of art for temperature proxy. No proxy data comes close but of course their location makes them pretty useless of global temperature measurement. However, their resolution is so good, that it does pretty much constrain what might be global versus local events. If a temperature excursion appears at same time in both Greenland and Antarctica, then that is extremely good evidence of a global event., otherwise suspect regional.

Second, I worry about your “pure proxy” wishes – you do understand how these proxy records are created? Nonetheless, the Tingley/Huyber paper does this for you. Same basic results are other multiproxy studies though. Just be aware that it is in press and their methodology has not scrutinized by scientific community yet.